Surface instability in high surface area complex oxides: BaTiO₃ study

High quality BaTiO₃ powders that were synthesized with hydrothermal and solid state methods are characterized with respect to surface chemistry. Different characterization techniques are used to obtain a physical picture for the BaTiO₃ powders with respect to different synthesis routes and thermal histories. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) are used to understand the BaTiO₃ powders after heat and humidity treatments. Formation of amorphous and crystalline BaCO₃ in local heterogeneous regions depletes the surrounding surface of Ba ions to create larger areas that are Ti-rich. BaCO₃ formation and adventitious carbon adsorption occur extremely quickly on the surface of crushed single-crystal BaTiO₃ powder, but for manufactured powders, the degree of carbonate formation and the impact on surface stoichiometry varies with thermal history.